XBlock is a browser extension for X (formerly Twitter) and a small server that keeps your block lists. It's made by Matrice Technologies, in France, and its code is public on GitHub. This page says what it keeps, why, and how to have it deleted. The short version: no account, no email, no X password, and nothing about what you read.
Who you are, to XBlock
Nobody in particular. When you install the extension, it makes a random key in your browser and keeps it in Chrome's sync storage, so your lists follow you to your other computers. The extension sends that key with each request, and the server turns it into an ID with a one-way HMAC-SHA256. The server stores that ID, never the key. It also gives you a random display name, like “Brave Otter”, shown on the lists you share.
What the server keeps
- Your lists: the X handles you blocked with XBlock, the list's name and share code, and for curated lists a short note per account.
- Your allowed accounts: the handles you marked with the shield, so no list ever blocks them.
- Your subscriptions: which lists you follow, and the mode each one uses (Block on X, Mute on X, Hide or Blur).
- What XBlock blocked or muted for you on X, so a batch never does the same account twice.
- Your settings (whether block animations are on, for instance), when you joined and when you last connected.
- Public follower counts of X accounts that show up in feeds. They aren't tied to you: everyone shares them, so batches can start with the biggest accounts.
Lists are public by design: anyone with a list's share code can see the handles on it and the owner's random display name.
What it never sees
- Your X password, cookies or session. Blocks and mutes go from your browser straight to X.
- Your email address, real name or phone number. XBlock never asks.
- What you read, write, like or search on X, and your browsing history.
- Your direct messages.
What happens in your browser
On x.com, the extension reads who wrote each post, so it can add its buttons and apply your lists. When you block or mute, it calls X itself, on the session you already have, exactly as x.com would. Settings such as your choice of animation are kept in Chrome's storage.
Sharing and selling
We don't sell or rent any of it, show no ads, and use no analytics or third-party trackers, in the extension or on this website. The server runs on a machine we rent from Hostinger; that host is the only third party that handles the data.
Network logs
The server uses your IP address in memory to rate-limit abuse, and never writes it to its database. The XBlock server itself writes no request logs.
Keeping and deleting
Your data stays as long as you use XBlock. To delete it, send your key (shown in the extension's popup) to xblock.extension@gmail.com, and we delete everything tied to it: lists, subscriptions, allowed accounts and block history. Uninstalling the extension removes the key from your browser; without it, nobody can reach that data again.
Run your own
If you'd rather keep everything yourself, the server is open source and runs anywhere Docker does. The self-hosting guide shows how to build the extension against your own server.
Changes and contact
If this policy changes, the new version goes up on this page with a new date. Questions: xblock.extension@gmail.com.